MySQL created_by or updated_last-by

I've been giving the task of taking SQL DDL from data modeler and to transcribe it into mySQL for an internship. The only thing I cannot figure out is how to take

Created_By VARCHAR2(30) DEFAULT USER, 

and turn that into sql my resolution was just to do a trigger but now the trigger doesn't work

    /* Triggers for User Creation */
DELIMITER //
CREATE TRIGGER menu_creator_tr 
BEFORE INSERT ON Menu 
FOR EACH ROW BEGIN
    NEW.Created_By = USER();
END 
DELIMITER;

it states that NEW.Created_By is missing a colon. I am very confused now. Just started learning sql and so i am lost. Some help for both problems is what I am looking for to learn, but a help on either or will help me finish this. I really need to know this though for I have more columns that are similar.